1. Field of the Invention
The present invention relates to a transferring device, a method and structure for cleaning the transferring device, and an image forming apparatus that includes the transferring device.
2. Discussion of Background
A transferring device transfers toner images formed on an image bearing member to a sheet at a transferring nip between a transferring member, e.g. a transferring roller, and the image bearing member. In this transferring device, toner residue may be picked up on the back side of a sheet at the transferring nip.
Before the sheet is transferred to the transferring nip, toner on the surface of the image bearing member are transferred to the surface of the transferring member. Next, this toner on the surface of the transferring member is transferred to the back side of the sheet.
Japan Laid-Open Patent Publication no. 2006-003859 shows an image forming apparatus that prevents toner residue.
This image forming apparatus transfers toner on the surface of an intermediate transferring belt, serving as an image bearing member, to the front surface of sheet at the second transferring nip which is formed between the intermediate transferring belt and a second transferring roller, serving as a transferring member.
A cleaning blade contacts the surface of the second transferring roller. The cleaning blade removes the toner on the surface of the second transferring roller after passing the second transferring nip, and it prevents the toner on the surface of the second transferring roller from going into the second transferring nip. Thus, it prevents the toner residue on the back side of sheet.
In addition, in this image forming apparatus, a solid lubricant made of zinc stearate is supplied to the surface of the second transferring roller by a rotating lubricant supplying brush.
By applying the lubricant to the surface of the second transferring roller, the adhesion of the toner to the surface of the second transferring roller becomes weak, and the toner removal characteristics from the surface of the second transferring roller improves.
Recently, spherical toner, which has a relatively small diameter and high average roundness, has been used in place of crushed toner, which has a relatively big diameter and a low average roundness. In image forming apparatuses using spherical toner, the spherical toner easily passes through the nip between the surface of the second transferring roller and the cleaning blade, and it is difficult to prevent the occurrence of toner residue on the back side of sheets.